The present invention relates to starter motors used to crank internal combustion engines. More particularly, the present invention relates to a starter motor which integrates the epicycle gear train and the one-way roller clutch into an axially compact unit.
Internal combustion engines conventionally use electric starter motors for cranking. Electric starter motors became popular in the late 1900's and early 1910's and incorporated a one-way clutch fitted to the end of the armature shaft of the starter. The one-way clutch is used during engine cranking to transmit torque and motion from the electrical motor to the output shaft and pinion and to the ring gear on the engine crankshaft. By only operating in a single direction, the clutch prevents the electric motor from being rotated too fast when driven by the engine after it has been successfully started. Typically the one-way clutch is in the form of a roller clutch that provides extra protection when a large load is transmitted from the engine to the starter by any means. The motor armature shaft is connected directly with the output shaft via the one-way clutch.
As engine size and cylinder compression increased with advances in engine technology, an epicycle or planetary gear train was added to the starter motor arrangement to increase torque. According to known design, the epicycle gear train is separate from the one-way roller clutch assembly. By having two separate assemblies the overall length of the starter is inherently long, thus creating engine compartment packaging problems. In addition, the greater length of the starter, which is a direct result of the arrangement of the two separate assemblies, results in vibration and fatigue failures.